The ability to accurately determine the position of a device within the body currently yields a considerable benefit for at least one medical procedure. This is the electrophysiological mapping of the heart. Such mapping frequently permits the location and treatment of the neurological disorder that has given rise to a heart arrhythmia. In order to accurately perform this mapping a transceiver head must be introduced into the heart by way (in part) of the femoral artery. The position and orientation of this transceiver head must be accurately monitored.
In order to perform this monitoring a set of orthogonally positioned inductive coils are fixed at the transceiver head and conductively connected through the catheter to the outside of the body, where the current in each of the inductive coils can be read. Cooperating with these coils, powerful magnets are arrayed about the imaging station, so that the current through each coil is dependent on its orientation relative to the magnetic field created.
Heretofore, the manufacture of the unit in which the coils reside has been a challenging and expensive operation. Each coil was soldered to a pair of wires and adjusted so that its position was generally correct. Next the coils and attached wires are gently placed into a polymer tube, which is then filled with epoxy to retain the coils in their generally mutual orthogonal positions and to retain the tube in its protective position.
Performing this method resulted in many problems. First, there was the difficulty in maintaining the mutually orthogonal orientation of the inductive coils during their insertion into the tube and the filling of the tube with epoxy. Also, air pockets would sometimes form as the epoxy was being introduced into the tube.
Another difficulty in the manufacture of a device bearing orthogonally oriented inductive coils is the achievement of true orthogonal orientations. At the fraction of a millimeter scales required to create a device that can be moved through small blood vessels, it is not easy to ensure that each inductive coil is placed within 89.9° and 90.1° of the orientation of the others.